Nik Wallenda walked on a high wire 500ft (152m) up between two Chicago towers in gusting winds, without a safety harness, blindfolded. But is his fearlessness natural or learned, asks Tom de Castella.

The Answer

Not clear whether babies have innate fear of heights

Some adults seem not to fear heights

Training instils confidence that you will not fall

Tests of crawling infants have shown them to avoid an apparent (but glass-covered) precipice. For a long time it was supposed that they did this because of instinctive fear. But a review of the research by academics at New York and Rutgers universities has come to a different conclusion. The infants avoid crawling over what looks like a high drop, not by being fearful but because of "the relations between their own bodies and skills and the relevant properties of the environment that make an action such as descent possible or impossible".

In layman's speak, the infants sensed that their arms and legs weren't equipped to navigate such a big drop, so avoided it. The New York and Rutgers researchers noted that younger infants without good motor skills did go over the virtual precipice. Older infants with more co-ordination avoid the drop and their facial expressions - often smiling and never crying - suggest they were not stressed. It's "very sensible" of the babies to avoid big drops, says Dr Peter Hayward, a consultant clinical psychologist. "But it might not be fear."

The key tests are on babies because in later life cultural factors come into play. As babies can't explain their motivations to researchers a definitive answer may never be possible.

Wallenda comes from a dynasty of tightrope walkers. But the fearlessness may simply have come from growing up around wire walking rather than any genetic advantage.

Wire walkers do build up their confidence, says Tim Roberts of the National Centre for Circus Arts. A rookie starts on a wire 30cm above the ground. The height is gradually increased and safety systems removed. You learn not to look down. "You can't keep your balance if you look down. A wire walker will look at the platform at the other end." Wallenda would have been acutely aware of the risks. In 1978 his great-grandfather Karl fell to his death trying to walk between two buildings in Puerto Rico.

Image copyrightLIONEL BONAVENTURE

Even for the fearful layman there are helpful techniques, says Hayward, who has a phobia of heights. "The best way to overcome it is by practice." He deliberately exposes himself to fear by going on the London Eye or the Emirates Air Line cable car. When he finds himself gripping the seat he removes his hand and reminds himself that holding on would achieve nothing. "These safety behaviours reinforce the fear," he says.